Oil production with steam



A ril 4, 1967 W. B. BELKNAP OIL PRODUCTION WITH STEAM Filed June 4, 1964INVE OR. W. B. BE NAP A T TORNEVS United States Patent 3,312,281 OILPRODUCTION WITH STEAM William B. Belknap, Bartiesville, 0kla., assignorto Phillips Petroleum Company, a corporation of Delaware Filed June 4,1964, Ser. No. 372,553 5 Claims. (Cl. 166-40) This invention relates toa process and apparatus for producing oil from a subterraneanoil-bearing stratum using steam.

Heavy crude oil has been produced by the so-called huff and puff methodin certain areas of the United States. This method comprises injectingsteam into the oil-bearing stratum thru a well tubing in a single drillhole for a substantial period such as to 30 days or more, to cause oilto flow into the well, then terminating steam injection, inserting apump and pumping rod into the tubing and pumping the oil from the wellwhich has flowed thereinto during the steaming period. After producingthe available oil from the bottom of the well, the steaming and pumpingsteps are repeated. The removal and reinsertion of the rod string andpump is time consuming and expensive. In my copending application, S.N.350,- 254, a method and apparatus are disclosed for avoiding withdrawaland reinsertion of the rod string and pump from the tubing string forthe steam injection phase of the huff and puff process.

This invention is concerned with another method and means for operatingthe huff and puff process without the necessity of removing andreplacing the downhole pump and rod string.

Accordingly, an object of the invention isvto provide a process andapparatus for producing oil from an oil-bearing subterranean stratumwith steam which avoids the use of a downhole pump. Another object is toprovide a process and apparatus for producing oil from such a stratumwhich eliminates pumping and utilizes steam for lifting the oil thru thetubing string. Other objects of the invention will become apparent toone skilled in the art upon consideration of the accompanyingdisclosure.

A broad aspect of the invention comprises injecting steam from a steamgenerator at ground level thru a tubing string into an oil-bearingsubterranean stratum so as to render the oil less viscous and cause sameto flow into the well; terminating the injection of steam thru thetubing string and opening same to the production of oil; injecting steaminto the annulus from the steam generator between the tubing string andthe casing and admitting steam from the annulus to the tubing string soas to cause oil to rise in the tubing, aerate same, and gas-lift the oilthru the tubing string to a production line connected therewith.Preferably, a series of gas-lift valves are placed in special tubingcollars as the tubing is run. These gas-lift valves are positionedseveral hundred feet apart toward the lower end of the tubing stringbelow the static fluid level. The tubing string functions as an eductiontube. Instead of having to depress the unaerated fluid to the level ofthe bottom of the tubing before gas may enter and aerate the fluid inthe eduction tube, gas enters the tubing at each valve, in turn,aerating the fluid thereabove and starting fluid flow thru the tubingbefore the fluid in the annulus is depressed to the lower end of thetubing. This results in correspondingly lower starting pressures. Afterflow has been established throughout the full length of the eductortube, the pressure conditions within the downward and ascending streamsof gas are such that the valves remain closed and all steam flows to thebottom of the eductor tube before mixing with the ascending streams ofliquid and vaporous oil.

Various types of gas-lift valves are available commercially. Some admitgas from the annulus into the tubing while others admit gas from thetubing into the annulus 3,312,281 Patented Apr. 4, 1967 where productionis to be effected thru the annulus. In the instant process productionthru the tubing is preferred.

In operation without gas-lift valves, the steam pressure in the annulusforces the liquid oil up the tubing until the liquid level in theannulus is depressed to the bottom of the tubing at which stage steamenters the lower end of the tubing and aerates the liquid in the tubingto effect gas lifting thereof.

The invention utilizes a steam' boiler or generator at ground leveladjacent the well head which is connected by a conduit with the wellannulus. A production line or conduit connecting with the tubing stringalso connects by means of a cross-over conduit with the conduit leadingfrom the steam generator to the annulus. A valve in this cross-overconduit directs the steam either into the annulus or into the tubingstring as desired. Other control valves in the connecting conduitspermit alternate steam injection and steam lifting of the produced oilinto the production line.

A more complete understanding of the invention may' be had by referenceto the schematic drawing which is an elevation of a preferredarrangement of apparatus for performing the invention.

1 Referring to the drawing, a viscous oil-bearing stratum 10 ispenetrated by a well 12 which is provided with a casing 14 and a tubingstring 16 forming an annulus 18 with the casing. Tubing string 16 isprovided with a series of gas-lift valves 20 positioned at levelsseveral hundred feet apart in the lower section of the tubing stringbelow the static fluid level. These valves selectively admit steam tothe tubing string from the well annulus.

Valves 20 are adapted for high temperature service 7 since the steamtemperature may reach temperatures as high as 700800 F.

A steam boiler or generator 22 is connected by means of a conduit 24with annulus 18 thru well head 26 and is provided with a cut-off valve28. A production line or conduit 30 connects with tubing string 16 at orabove the well head and is provided with a pair of spaced-apart cutoffvalves 32 and 34. A cross-over conduit 36 containing valve 38 connectsconduit 24 upstream of valve 28 with production line 30 intermediatevalves 32 and 34. This arrangement permits injection of steam into theformation thru tubing 16 by closing valves 28 and 34 and opening valves32 and 38 so that steam passes thru a portion of conduit 24, conduit 36,and production line 30 into the well tubing. The valve arrangement alsopermits injection of steam thru the well annulus so as to educt oil fromthe bottom of the well into production line 30 thru tubing string 16 bypositioning valves 32 and 34 in the open position, closing valve 38, andopening valve 28.

The injection of steam thru annulus 18 is commenced after suflicientsteaming of the stratum has been effected to produce a substantialamount of oil in the bottom of the well such as is illustrated by oillevel 40. The steam pressure applied in the annulus on the surface ofthe oil, with conduit or line 30 open to flow, depresses the oil leveland causes oil to rise in tubing 16 so that it passes .the lower-mostgas-lift valve and actuates the valve so as to admit steam at thislevel, thereby aerating the oil above the valve with steam and producinga lifting action on the column of fluid within tubing 16. As oilsuccessively passes the upper gas-lift valves, these valves function ina similar manner and the oil is lifted thru the tubing string withsubstantially less pressure than would be required without the use ofthe gas-lift valves.

A gas-lift valve is actuated by a predetermined fluid pressure or headat the valve level so as to open when said pressure is reached and admitsteam to the tubing to aerate the liquid oil therein. This aerationreduces the pressure head in the tubing at the valve level and causesthe valve to close until the head is again built up to the requiredopening pressure. Small holes in the tubing collars at selected levelsalso function as gas-lift valves, but

are not the full equivalent of such valves as the holes are enlarged bycorrosion and/ or erosion and eventually render the tubing stringinoperative.

By proper use of packers, dual production zones may be produced bysteaming and gas lift from steam injected thru a common annulus.

After the flow of oil thru production line 30 reaches a selectedminimum, the valves in the conduit system connected with steam generator22 are reversed and steam is again injected thru tubing 16 into thestratum so as to further heat and produce oil therefrom. The steamingand steam-lift steps are repeated as long as oil production from thestratum around the Well is profitable.

In producing viscous oil from a sand formation at a depth of about 3200,steam at a temperature in the range of 600 to 700 F. is injected at apressure in the range of 1500 to 2500 p.s.i.g. for an extended period ofat least 15 and up to 100 hours or more so as to produce a substantialamount of liquid oil in the bottom of the well. The injection of thesteam thru the tubing from the steam generator is then terminated andsteam at reduced pressure is injected into the annulus with the tubingstring open to the production line. The steam pressure on the oil in theannulus causes the oil to rise in the tubing string so that the oil inthe annulus falls to a level below the upper-most steam-lift valveresulting in a pressure differential between the steam in the annulusand the oil in the tubing which causes steam to be injected thru saidvalve thereby steam aerating the oil in the tubing and producing aneduction effect on the fluid column in this tubing. At this time, thesteam injection and gas-lift steps are repeated in the same order.

A packer can be installed packing off the well bore annulus below allgas-lift valves in which case oil in the annulus when packer isinstalled is produced into tubing through the lowermost valve. Steamenters the tubing at successively lower valves as previously describedwhen no packer is used.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

I.clairn:

1. Apparatus for producing oil from an oil-bearing subterranean stratumwhich comprises in combination:

(a) a casing communicating with said stratum from a well head;

(b) a tubing string within said casing forming an annulus therewithextending from said well head at least to the level of said stratum,said tubing string being free of a pump;

(c) a series of gas lift valves in said tubing string below the staticfluid level, each being positioned at a substantially different levelfor injecting steam to said tubing string from said annulus;

(d) a steam generator at ground level near said Well head;

(e) a first conduit connecting with said tubing string at the Well head;

(f) a second conduit connecting with said annulus ad- .jacent the wellhead and with said steam generator;

(g) a pair of spaced-apart flow control valves in said first conduit;

(h) a flow control valve in said second conduit;

(i) a third conduit connecting said second conduit at a pointintermediate the valve of (h) and said generator with said. firstconduit at a point intermediate the valves of (g); and

(j) a flow control valve in said third conduit.

2. Apparatus for alternately injecting steam thru a well into anoil-bearing subterranean stratum and steam lifting oil produced by thesteam injection comprising in combination:

(a) concentric casing and tubing strings connecting a well head withsaid stratum providing an annulus therebetween;

(b) a gas lift valve positioned at each of several levels in said tubingstring for injecting steam into said tubing from said annulus;

(c) a steam generator at ground level adjacent said well head;

(d) conduit means for passing steam from said generator to said tubingstring and to said annulus;

(e) valve means in said conduit means for alternately separately passingsteam to said annulusand to said tubing string; and

(f) means for passing produced oil from said tubing string to aproduction line when steam is being injected into said annulus.

3. A process for producing oil from an oil-bearing stratum thru a welltherein provided with a casing and a tubing string, which comprises thesteps of:

(a) providing said tubing string with gas lift valves at selectedspaced-apart levels beginning near the level of said stratum andinjecting superheated steam at high pressure from a steam generator intosaid stratum thru said tubing string for an extended period so as tocause hot oil to flow into said well from the surrounding stratum;

(b) thereafter, terminating the injection of steam thru said tubingstring and injecting steam from said generator into the annulus formedby said tubing and casing;

(-c) injecting steam at substantially less pressure than in step (a)from said annulus thru said gas lift valves into said tubing stringprogressively at a series of different levels therein beginning at thelowermost as the liquid oil passes each level so as to lift said oilthru said tubing while maintaining said tubing open to flow to aproduction line; and

(d) repeating steps (a), (-b), and (c).

4. The process of claim 3 wherein said stratum bears a low gravityviscous crude oil.

5. The process of claim 3 wherein said stratum is a tar sand.

References Cited by the Examiner UNITED STATES PATENTS 2,197,064 4/1940Aucoin 103-233 2,305,250 12/1942 Garrett et al 103-233 2,881,838 4/1959Morse et al 166-40 3,126,961 3/1964 Craig et al. 166-40 FOREIGN PATENTS511,768 8/1939 Great Britain.

CHARLES E. OCONNELL, Primary Examiner.

ERNEST R. PURSER, Examiner.

S. J. NQVOSAD Assistant Examiner.

2. APPARATUS FOR ALTERNATELY INJECTING STEAM THRU A WELL INTO ANOIL-BEARING SUBTERRANEAN STRATUM AND STEAM LIFTING OIL PRODUCED BY THESTEAM INJECTION COMPRISING IN COMBINATION: (A) CONCENTRIC CASING ANDTUBING STRINGS CONNECTING A WELL HEAD WITH SAID STRATUM PROVIDING ANANNULUS THEREBETWEEN; (B) A GAS LIFT VALVE POSITIONED AT EACH OF SEVERALLEVELS IN SAID TUBING STRING FOR INJECTING STEAM INTO SAID TUBING FROMSAID ANNULUS; (C) A STEAM GENERATOR AT GROUND LEVEL ADJACENT SAID WELLHEAD; (D) CONDUIT MEANS FOR PASSING STEAM FROM SAID GENERATOR TO SAIDTUBING STRING AND TO SAID ANNULUS; (E) VALVE MEANS IN SAID CONDUIT MEANSFOR ALTERNATELY SEPARATELY PASSING STEAM TO SAID ANNULUS AND TO SAIDTUBING STRING; AND (F) MEANS FOR PASSING PRODUCED OIL FROM SAID TUBINGSTRING TO A PRODUCTION LINE WHEN STEAM IS BEING INJECTED INTO SAIDANNULUS.
 3. A PROCESS FOR PRODUCING OIL FROM AN OIL-BEARING STRATUM THRUA WELL THEREIN PROVIDED WITH A CASING AND A TUBING STRING, WHICHCOMPRISES THE STEPS OF: (A) PROVIDING SAID TUBING STRING WITH GAS LIFTVALVES AT SELECTED SPACED-APART LEVELS BEGINNING NEAR THE LEVEL OF SAIDSTRATUM AND INJECTING SUPERHEATED STEAM AT HIGH PRESSURE FROM A STEAMGENERATOR INTO SAID STRATUM THRU SAID TUBING STRING FOR AN EXTENDEDPERIOD SO AS TO CAUSE HOT OIL TO FLOW INTO SAID WELL FROM THESURROUNDING STRATUM; (B) THEREAFTER, TERMINATING THE INJECTION OF STEAMTHRU SAID TUBING STRING AND INJECTING STEAM FROM SAID GENERATOR INTO THEANNULUS FORMED BY SAID TUBING AND CASING; (C) INJECTING STEAM ATSUBSTANTIALLY LESS PRESSURE THAN IN STEP (A) FROM SAID ANNULUS THRU SAIDGAS LIFT VALVES INTO SAID TUBING STRING PROGRESSIVELY AT A SERIES OFDIFFERENT LEVELS THEREIN BEGINNING AT THE LOWERMOST AS THE LIQUID OILPASSES EACH LEVEL SO AS TO LIFT SAID OIL THRU SAID TUBING WHILEMAINTAINING SAID TUBING OPEN TO FLOW TO A PRODUCTION LINE; AND (D)REPEATING STEPS (A), (B), AND (C).